Input: uinput - add UI_GET_VERSION ioctl

This ioctl is the counterpart to EVIOCGVERSION and returns the
uinput-version the kernel was compiled with.

Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>